Establishing "large-contact-area" interfaces of sensitive nanostructures with microbes and mammalian cells will lead to the development of valuable tools and devices for biodiagnostics and biomedicine. Chemically modified graphene (CMG) nanostructures with their microscale area, sensitive electrical properties, and modifiable chemical functionality are excellent candidates for such biodevices at both biocellular and biomolecular scale. Here, we report on the fabrication and functioning of a novel CMG-based (i) single-bacterium biodevice, (ii) label-free DNA sensor, and (iii) bacterial DNA/protein and polyelectrolyte chemical transistor. The bacteria biodevice was highly sensitive with a single-bacterium attachment generating approximately 1400 charge carriers in a p-type CMG. Similarly, single-stranded DNA tethered on graphene hybridizes with its complementary DNA strand to reversibly increase the hole density by 5.61 x 1012 cm(-2). We further demonstrate (a) a control on the device sensitivity by manipulating surface groups, (b) switching of polarity specificity by changing surface polarity, and (c) a preferential attachment of DNA on thicker CMG surfaces and sharp CMG wrinkles.

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Nonspecific binding (NSB), a random adsorption of biocomponents such as proteins and bacteria on noncomplementary materials, is one of the biggest problems in biological applications including biosensors, protein chips, surgical instruments, drug delivery, and biomedicine. Polyoxyethylene sorbitan laurate (TWEEN), a commercially available chemical with aliphatic ester chains, has shown promise as a medical material and in overcoming problems associated with NSB. [1][2][3][4] However, stability during solution-based processing and uniformity of the materials that have TWEEN coating on flat substrates or nanomaterials using the selfassembled-monolayer (SAM) method has been an important issue. Further, biocompatible materials with high strength are important for several medical applications including stents, nail implants, and strong invasive instruments. Here, we present the production of a free-standing ''paperlike'' material composed of TWEEN and reduced graphene oxide (RGO) platelets and obtained by simple filtration of a homogeneous aqueous colloidal suspension of TWEEN/RGO hybrid. The ''TWEEN paper'' was highly stable in water without leakage of TWEEN and is compliant and sufficiently robust to be handled by hand without breaking. Furthermore, the TWEEN paper was noncytotoxic to three mammalian cell lines and biocompatible, inhibiting nonspecific binding of Gram-positive bacteria.[5] In contrast, RGO paper without TWEEN showed nonspecific bacterial binding.TWEEN is composed of three chemical parts (Fig. 1a): aliphatic ester chains that can prevent NSB of biomolecules, three-terminal hydroxyl groups that are hydrophilic and can be chemically modified for further applications, and an aliphatic chain that can easily be adsorbed on a hydrophobic surface by noncovalent interaction. Protein microarrays on flat substrates with SAM of TWEEN [4] and highly sensitive biosensors, [1][2][3]

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Because of the edge states and quantum confinement, the shape and size of graphene nanostructures dictate their electrical, optical, magnetic and chemical properties. The current synthesis methods for graphene nanostructures do not produce large quantities of graphene nanostructures that are easily transferable to different substrates/solvents, do not produce graphene nanostructures of different and controlled shapes, or do not allow control of Gn dimensions over a wide range (up to 100 nm). Here we report the production of graphene nanostructures with predetermined shapes (square, rectangle, triangle and ribbon) and controlled dimensions. This is achieved by diamond-edge-induced nanotomy (nanoscalecutting) of graphite into graphite nanoblocks, which are then exfoliated. our results show that the edges of the produced graphene nanostructures are straight and relatively smooth with an I D /I G of 0.22-0.28 and roughness < 1 nm. Further, thin films of Gn-ribbons exhibit a bandgap evolution with width reduction (0, 10 and ~35 meV for 50, 25 and 15 nm, respectively).

Transmission electron microscopy (TEM) of hygroscopic, permeable, and electron-absorbing biological cells has been an important challenge due to the volumetric shrinkage, electrostatic charging, and structural degradation of cells under high vacuum and fixed electron beam.(1-3) Here we show that bacterial cells can be encased within a graphenic chamber to preserve their dimensional and topological characteristics under high vacuum (10(-5) Torr) and beam current (150 A/cm(2)). The strongly repelling π clouds in the interstitial sites of graphene's lattice(4) reduces the graphene-encased-cell's permeability(5) from 7.6-20 nm/s to 0 nm/s. The C-C bond flexibility(5,6) enables conformal encasement of cells. Additionally, graphene's high Young's modulus(6,7) retains cell's structural integrity under TEM conditions, while its high electrical(8) and thermal conductivity(9) significantly abates electrostatic charging. We envision that the graphenic encasement approach will facilitate real-time TEM imaging of fluidic samples and potentially biochemical activity.

Sodium hydride's ability to convert graphene oxide (GO) to reduced graphene oxide (RGO) and deprotonate methanol to the methoxy ion is applied to the preparation of a stable RGO dispersion in methanol. The process is extremely fast with high yield and produces RGO with a high density of sp2 carbon atoms. RGO sheets (see image) are characterized electrically and spectroscopically.

With the strict regulations of present times, chemical oxidation holds tremendous potential for destructive treatment of hazardous wastes which are resistant to biological oxidation. Fenton's reagent has proved to be an inexpensive and powerful oxidant which has been shown to oxidize a wide variety of organics. In this paper, 2,4 dinitrotoluene (2,4 DNT) was chosen as a model compound following previous work where 2,4 DNT was subjected to oxidation by hydrogen peroxide in the presence of medium power UV source. Various factors that are important to optimize the oxidation of organics were studied. The effect of aeration, step dosing and the role played by the ferric ions on oxidation of 2,4 DNT were verified in this experimental study. The results of our work show that 2,4 DNT can be effectively oxidized in aqueous solutions with Fenton's reagent. At a H2O2: DNT: Fe2+ ratio of 20:1:2.5 (molar), 2,4 DNT was completely removed in 5 hours. Finally, the results and the reaction intermediates of the oxidation of 2,4 DNT with Fenton's reagent vis-a-vis the H2O2/UV system are discussed.